Conventional hot water tanks are subject to corrosion during use. To prevent this corrosion, sacrifical anodes, normally constructed of magnesium, aluminum or zinc, are inserted into the tank. The sacrificial anode is slowly consumed during the protection process and results in the production of an electrical current. As the anode is slowly depleted, the simultaneously generated electrical current cathodically protects the tank.
The service life of the anode is primarily dependent upon the amount of the electrical current flow generated by the anode in cathodically protecting the tank. In many fresh water supplies, particularly those having a high mineral content, the current flow is relatively high, resulting in a corresponding decrease of the useful life of the anode.
A resistor type anode has been constructed in the prior art in order to limit the amount of current flow and, thereby extend the useful life of the anode. Referring to FIG. 1, a conventional prior art resistor anode construction is shown which utilizes a standard barrel bodied, pigtailed type carbon resistor 10 having pigtails or copper wire connections 12 and 14 which must be electrically connected to the unit by soldering. The anode 16 is cylindrically shaped, has a central core wire 18 along the longitudinal axis and includes a machined neck portion 20 of lesser diameter than the main portion of the anode 16. An insulator sleeve 22, having a cylindrically shaped inner surface with a diameter substantially equal to the outer diameter of the neck portion 20, is inserted over the neck portion 20 of the anode 16.
A steel anode cap 24 is provided to fit snugly over and around the outside portion of the plastic insulating sleeve 22. The resistor 10 is positioned in a bore 25 which is defined in the neck portion 20. The bore 25 has a volume greater than that of resistor 10 in order to comfortably receive the resistor 10. The pigtail 12 of resistor 10 is then connected either to the inner portion of the steel cap 24 or to a brass disc 26 which may be force-fitted into the cap 24 and electrically connected therewith. The other pigtail 14 of the resistor 10 is electrically connected by soldering to the inner core wire 18.
While generally effective for the purpose intended, the prior construction utilizing the barrel type resistor 10 with pigtails 12 and 14, had several drawbacks. For example, it was somewhat difficult and time consuming to electrically solder both ends of the pigtail to the disc 26 and core wire 18, respectively. Also, this type of construction sacrificed ruggedness, since the resistor 10 (which is free to move within the anode 16) and its connections 12 and 14 could become easily damaged or disconnected during assembly and shipment, or as a result of moisture accumulated in the location surrounding the resistor during use.